Energy balance with Battery backup

[solarysnrg]

In a system connected to the grid with backup batteries, the energy balances are not consistent!

EDirUse+EBatCh+E_Grid > E_Avail ( much greater )

[Bruno Wittmer]

The variable EDirUse containds already E_Grid. It represents all the energy that does not go through the storage:

E_Avail = EDirUse + EBatCh

[solarysnrg]

The variable EDirUse containds already E_Grid. It represents all the energy that does not go through the storage:

E_Avail = EDirUse + EBatCh

 

But is non correct! If the energy is sold to the grid it is not directly used;

[Bruno Wittmer]

This is a matter of definition.

'Direct Use' in this context just means that the energy did not go through the battery.

You can compute the energy that went directly from solar to self-consumption by subtracting E_Grid from this value.

[Mariyam]

On 2/24/2022 at 11:05 AM, Bruno Wittmer said:

This is a matter of definition.

'Direct Use' in this context just means that the energy did not go through the battery.

You can compute the energy that went directly from solar to self-consumption by subtracting E_Grid from this value.

Could you please elaborate on this further?

[André Mermoud]

The energy provided by the Solar system may be used:

- either for charging the battery,

- or (mainly when the battery is full, but this depends on the kind of system) it is directly used, either for feeding the grid or the user's needs  (this also depends on the system kind).   This is what is named "E Direct Use",  as a complement to "ECharging (from PV)".